I've been doing some experimenting for the past couple weeks since I've switched to fleece, and I've decided that mattress pads work the best as an absorbent layer on bottom. A "full" size mattress is 54" and it fits a standard C & C cage perfectly when folded in half (27")- you just have to cut off the stretchy part that is meant to hold it to the mattress.
Before this I have tried using terrycloth and puppy pads. The terrycloth got too frayed and I needed at least two layers of it, so it took a lot of time to arrange it after each cleaning. The puppy pads work great, but it is too expensive to keep buying new ones. Mattress pads are wonderful because they fold into place easily and don't require a lot of finessing like the terrycloth did. A mattress pad folded over once provides a lot of absorbency, and it has some fluff to keep the floor of the cage soft and comfy.
I just thought I'd share this info in case it is useful to someone!
Before this I have tried using terrycloth and puppy pads. The terrycloth got too frayed and I needed at least two layers of it, so it took a lot of time to arrange it after each cleaning. The puppy pads work great, but it is too expensive to keep buying new ones. Mattress pads are wonderful because they fold into place easily and don't require a lot of finessing like the terrycloth did. A mattress pad folded over once provides a lot of absorbency, and it has some fluff to keep the floor of the cage soft and comfy.
I just thought I'd share this info in case it is useful to someone!